No Need for RADAR to Track a Plane

On 17 March I was travelling on a US domestic flight from Dallas to New York (AA718, Boeing MD-80). The plane had onboard wifi internet access from Gogo Inflight Internet. My mobile phone, a Google Nexus One, had GPS reception and sent its location to the Google servers via Google Maps and Google Latitude. Latitude is a Google protocol for sharing your location with selected contacts. I had configured my Latitude account to story my location history.
How does Gogo Inflight work? Not via a satellite connection, but via transceivers on the ground with which the plane makes contact when at cruising altitude.